Test plates for chemical or biochemical analysis which contain a plurality of individual wells or reaction chambers are well known laboratory tools. Such devices have been employed for a broad variety of purposes and assays, and are exemplified in U.S. Pat. Nos. 4,734,192 and 5,009,780, for example. Microporous membrane filters and filtration devices containing the same have become especially useful with many of the recently developed cell and tissue culture techniques and assays, especially in the fields of virology and immunology. Multiwell plates, used in assays, often use a vacuum applied to the underside of the membrane as the driving force to generate fluid flow through the membrane.
Typically, a 96-well filtration plate is used to conduct multiple assays simultaneously. In the case of multiwell products, there is a need to deal with liquid collection, removal and recovery in an effective manner. In particular, high throughput applications, such as DNA sequencing, PCR product cleanup, plasmid preparation, drug screening and sample binding and elution require products that perform consistently and effectively. If droplets are allowed to remain in proximity to the purified sample for longer than necessary, a variety of deleterious effects may result, including possible contamination of purified sample.
One such filtration device commercially available from Millipore Corporation under the name “MULTISCREEN3/4” is a 96-well filter plate that can be loaded with adsorptive materials, filter materials or particles. The MULTISCREEN device underdrain has a phobic spray applied in order to facilitate the release of droplets. More specifically, the MULTISCREEN device includes an underdrain system that includes a spout for filtrate collection This spout not only directs the droplets but also controls the size of the drops. Without the underdrain system, very large drops form across the entire underside of the membrane. The drop volume that can remain without such an underdrain is much larger than with such an underdrain. The spout is hydrophobically treated to enhance droplet release for quantitative collection.
It would therefore be desirable to provide an effective means for liquid collection in sample preparation devices such as multiwell arrays.
It would also be desirable to provide an effective means for removal of filtrate droplets from the underside of a membrane without requiring the addition of an underdrain system.